Elastic fastener

ABSTRACT

An elastic web of material has a multiplicity of stems extending from at least one side of the web. The web includes a first continuous layer of elastic material having a first side and a second side and a second layer of material. The second layer of material has a first side which faces the first side of the first layer and a second side from which the stems extend. The first and second layers of material are joined together. The second layer of material can be formed of thermoplastic material or melt processable polymeric material. The first and second layers of material are melt formed. They are joined by coextrusion or lamination to form a multiple layer sheet on which a multiplicity of stems are formed on at least the second layer by a process such as embossing the stems into the heated web using a patterned roll or mold.

CROSS-REFERENCE TO OTHER APPLICATIONS

[0001] This is a divisional of U.S. patent application Ser. No.09/508207, filed Mar. 8, 2000, which is a 371 of PCT/US98/20858, filedOct. 2, 1998, which is a continuation-in-part of U.S. patent applicationSer. No. 08/943482 filed Oct. 3, 1997, all of which are incorporated byreference.

FIELD OF THE INVENTION

[0002] This invention relates to webs, such as polymeric webs, having asurface with a multiplicity of features used for fastening or joining.Such features may be stems, loops and other surface features that canmechanically interlock with features, such as fibers or protrusions, onan opposing surface.

BACKGROUND

[0003] Hook and loop fasteners, such as those currently marketed underthe “Scotchmate” trademark by Minnesota Mining and ManufacturingCompany, St. Paul, Minn. (3M) are a known type of mechanical fastener.One alternative to a hook is a mushroom-shaped protrusion or stem whichcan also be used as a hermaphroditic mechanical fastener by engagingother protrusions or surface features rather than loops.

[0004] U.S. Pat. Nos. 4,056,593 and 4,959,265 disclose methods ofextruding polymeric webs with upstanding stems. In the hook structure ofU.S. Pat. No. 5,077,870, a single component thermoplastic resin isextruded onto a tool which has an array of cavities which, uponseparation from the resin, form an array of stems. The stems then arecalendered to produce a broader head (cap or mushroom head) at the topof the stem. U.S. Pat. No. 5,393,475 discloses a method of making astemmed web with stems on both sides using two different materials.

[0005] Despite current advances in the art, there is a need for stemmedwebs, such as mechanical fasteners, that have a wider variety ofproperties to meet more varied applications.

DISCLOSURE OF INVENTION

[0006] For purposes of this description, a stem refers to a protrusionfrom a surface, such as a web, regardless of the shape, length,length-to-width ratio, or other characteristics of the protrusionprovided that the stem can mechanically interlock or engage with amating surface having other features such as stems, loops or fibers. Astemmed web is a web having on at least one surface small structures orfeatures such as hooks and stems.

[0007] The present invention is a web of material having a plurality ofstems extending from at least one side of the web. The web includes atleast a first layer of material having a first side and a second sideand a second layer of material. The second layer of material has a firstside which faces the first side of the first layer and a second sidefrom which the plurality of stems protrude. The first and second layersof material may be, but need not be, joined together while one or bothof the layers are molten and before the molten layer or layers havecooled.

[0008] The first layer is formed from an elastic material and the secondlayer of material can be formed of thermoplastic material or meltprocessable polymeric material. The first layer of material differs fromthe second layer of material and in one embodiment the material formingthe first layer protrudes into and forms at least part of the stemsformed on the second layer.

[0009] In other alternative embodiments, both surfaces of the web canhave stems, and one or more of these stems can have caps. Additionallayers of material also can be formed and joined together with the firstand second layers.

[0010] The invention also includes a method of making a web of materialhaving a plurality of stems. The method includes selecting a firstelastic material for a first layer of material and selecting a secondmaterial for a second layer of material. The first and second layers ofmaterial are melt formed. The first and second layers of material arejoined to form a two-layer sheet. Next, a plurality of stems are formedon at least the second layer of material.

[0011] The stems can be formed by pressing the multiple layer sheetagainst at least one temperature controlled surface containing an arrayof holes to form an array of stems. Caps can subsequently be formed onthe tips of the stems by pressing the stems against a heated surface toform caps on the tips of the stems.

[0012] Alternatively, the stems can be formed by extruding multiplelayers of a thermoplastic or melt processable material through a shapeddie to form a multiple layer sheet having a plurality of raised ribs onat least one surface. A plurality of sharp edges is passedperpendicularly through the ribs, and the multiple layer sheet isstretched to separate each rib into a plurality of stems. The stems canbe formed with a hooked shape or subsequently pressed against a heatedsurface to form a hook or capped stem.

[0013] The melt forming step can include simultaneously melt forming thefirst and second layers of material. The joining step can include: (a)joining together the first and second layers before any layer hascooled; (b) laminating the first and second layers; and/or (c)incorporating one or more reactive tie layers between the first andsecond layers. Melt forming can be accomplished by coextruding the firstand second layers of material.

[0014] The inventive web can be stretched to surround an object or bodyto be fastened, secured or wrapped and relaxes to provide a constanttension that conforms to that body or object. It also exhibitssubstantially continuous fastening capability along its entire length.Instead of being formed from an elastic material having fastening meansonly at the ends of an elastic web, these continuous fasteningconstructions can have fastening means across or along the entire lengthand width of elastic web. Benefits realized from these constructions areat least two-fold: (1) such continuously-functional webs could be cutinto any useful size and geometry and exhibit functionality, allowingfor among other things a tape-like packaging; and (2) suchcontinuously-functional webs would have more fastening capability perunit area.

BRIEF DESCRIPTION OF DRAWINGS

[0015] All of the figures are partial cross-sections of the inventiveweb material showing various embodiments of the stem and thecombinations of the first and second material layers, as follows:

[0016]FIG. 1. A construction in which the first, elastic layer protrudesthrough the second layer to form the stem.

[0017]FIG. 2 is an embodiment like FIG. 1 except that the stem has acrown or tip made of the second layer material.

[0018]FIG. 3 is an embodiment in which the stem comprises a core of thefirst, elastic, layer material and an outer sheath or surface of thesecond layer material.

[0019]FIG. 4 shows an embodiment in which the stem comprises mostly theupper or second layer material and just a small portion of the first,elastic, layer material protrudes into the base of the stem.

[0020]FIG. 5 is an embodiment in which the stem is made entirely of thesecond layer material.

[0021]FIG. 6 shows an embodiment like FIG. 5, with the additionalfeature that the second layer comprises a plurality of layers.

[0022]FIG. 7 depicts an embodiment of the inventive web with a pluralityof stems, prior to being stretch activated.

[0023]FIG. 8 depicts the same construction as FIG. 7 in the extendedstate after stretching and dislocation of the individual stems from eachother.

DETAILED DESCRIPTION

[0024] Mechanical fastener hook structures are one type of stemmed web.These fasteners have some type of hook, capable of engagement with aloop material formed, on a stem which, in turn, is formed on a web. Insome applications, the hook structures and base supports are made frommultiple components. In the present invention, these multiple componentsare formed together, such as by melt forming (such as extrusion) toenhance the performance properties of the mechanical fastener. Theseperformance enhancements depend on the selection of materials andinclude: hook strength, hook and stem flexibility, durability, wearresistance, loop retention, loop engagement, softness, appearance, peel,and shear strength. Selecting materials and configurations changes themechanical fastener properties for individual applications.

[0025] Another type of stemmed web has uncapped stem structures. Thestem surface can be self mating when the surface of the stems isauto-adhering, e.g., by application of an adhesive material to one ormore surfaces of the stemmed web.

[0026] Some properties that affect the performance include the thicknessof the layers of material, the stem construction (whether the stems areformed of one or more materials and the relative placement of thematerials if the stem is composed of more than one material), whether asingle layer or multiple layers are used, the stem density (number ofstems per unit area), the stem geometry (whether the stems areessentially straight, angled or have shaped hooks) and thecharacteristics of the second surface of the construction.

[0027] The multiple layer fastener includes at least two layers that areformed with at least one surface having an array of stems. The firstlayer of such fasteners will comprise an elastic material such that theconstruction overall will exhibit elastic character, i.e., may beelongated (by at least 5, preferably 10, more preferably 20 percent)from an initial state in at least one direction when subjected to astress (eg. tensile stress) and substantially returns to said initialstate upon the removal of the stress. The inventive web is considered tosubstantially return to its initial state or condition if there is sometensile set or stress relaxation which can be up to 50%, preferably lessthan 30%, more preferably less than 25%. The first layer may compriseany of the wide variety of known elastomeric materials including, forexample, elastomers such as natural or synthetic rubber, styrene blockcopolymers containing isoprene, butadiene, or ethylene(butylene) blocks,metallocene-catalyzed polyolefins, polyurethanes orpolydiorganosiloxanes. Other elastomers can be related to the followinggroups: polyesters, polyamides, polyolefins, block and star polymers.

[0028] The second layer of the stemmed web constructions may beinitially continuous. It and other additional layers, when present, canbe the same or can each be different from one another and from thematerial comprising the first elastic layer. For example any such secondor additional layer may comprise the same or different elastomericmaterial comprising the first layer, or any such layer may benon-elastomeric. One such layer also may be ductile and another may bestiff. Some examples of material types useful for the second and/or theoptional additional layers include polyolefins such as polypropylene orpolyethylene; other thermoplastics such as polystyrene, polycarbonate,polymethyl methacrylate, ethylene vinyl acetate copolymers, acrylatemodified ethylene vinyl acetate polymers, and ethylene acrylic acidcopolymers; pressure-sensitive adhesives such as acrylic, natural orsynthetic rubber, tackified styrene block copolymers, tackifiedpolydiorganosiloxane urea copolymer and amorphous poly(1-alkene); hotmelt adhesives such as ethylene-vinylacetate; ductile thermoplasticssuch as nylon or polyvinylchloride; non-tacky adhesives; as well asblends of these materials.

[0029] Multiple layers, such as more than three and typically as many asone hundred layers, can also result in new compositions of stem-surfacedweb constructions having properties that may be different from those ofthe individual materials used. Either or both the first or second layersor any additional layer also may comprise two or more strata of at leasttwo different materials, yielding multi-layer constructions with a widearray of composite characteristics.

[0030] Various materials also can be used to provide desiredcharacteristics on either or both sides of the web. Some examples ofthese include adhesive surfaces, surfaces that can provide an abrasiveor high friction surface, release surfaces that can provide a lowfriction surface, and active surfaces that provide a receptive surfacefor materials such as adhesives, coatings, or colorants to produce adurable image. Colorants can encompass a broad range of materials suchas inks in water, or inks in organic solvents, or inks that are composedof 100% active material. These inks can be cured by such methods asexposure to ultraviolet (UV) light or electrostatic graphic imaging.Coatings can include any number of materials either as a 100% solidsmaterial, or dissolved or dispersed in any combination of water andorganic solvents. One example would be a coating that permits thematerial to be printed by an ink jet printer.

[0031] Interlayer adhesion between the first and second layers(principal layers) or between any of the auxiliary layers where presentmay be enhanced by incorporating one or more reactive species into thelayers to create a reactive tie layer at the interface or byincorporating into the construction separate layers that have affinitiesto both principal layers. Such reactive species enhance interlayeradhesion by reacting at the interface of the respective layers. As such,most of the reactive species may be in the bulk of the layer and thusnot at the surface and useful for enhancing adhesion. Some polymers aremarketed that contain small amounts of grafted reactive moieties. Whenproperly matched, these materials effectively increase interlayeradhesion. Useful pairs include, for example, carboxylic acid/amine,maleic anhydride/amine, carboxylic acid and maleic anhydride/hydroxyl,maleate and maleic anhydride/double bond, carbodiimide/carboxylic acid,isocyanate/hydroxyl, amine/hydroxyl halide, ester/amine, ester/ester,ester/hydroxyl phenol, amide/ester, epoxide/hydroxyl or amine orcarboxylic acid or maleic anhydride, oxazoline/carboxylic acid or phenolor maleic anhydride and lactam/amine or acid ionomer.

[0032] Reactive tie layers may be continuous or discontinuous and may beelastomeric or non-elastomeric. The selection of an appropriate tielayer will depend upon the functionality desired of that tie layer, andsuch selection will be within the competence of the skilled artisan.Generally, reactive tie layers comprise a multi-segmented graft polymeror block copolymer comprising molecular segments that have preferentialaffinity for the material of the first layer or that of the secondlayer. Useful tie layer materials include, for example, ethylene acrylicacid block copolymer for enhancing the adhesion of a layer ofpolyethylene to a layer of polyacrylic acid, ethylene vinyl alcoholblock copolymer for enhancing the adhesion of a layer of polyethylene toa layer of polyvinyl alcohol, ethylene vinyl acetate block copolymer forenhancing the adhesion of a layer of polyethylene to a layer ofpolyvinyl acetate, ethylene methyl acrylate block copolymer forenhancing the adhesion of a layer of polyethylene to a layer ofpolymethylacrylate and polypropylene with grafted epoxy or maleicanhydride groups for enhancing the adhesion of a layer of polypropyleneto a layer of polyurethane. Relative layer thickness influences theproperties of the inventive elastic fastener construction. A thin layerof adhesive forming the outer layer of a stem and a stiff polymerforming a thick core of a stem yields a stem array that is more rigidthan that having a thick layer of adhesive over a thin stiff core. It isimportant, however, that the overall thickness of the elastic layers(i.e., the first, continuous elastic layer along with any other elasticlayers) is such that the overall construction exhibits elastic behavior.

[0033] By controlling the thickness, viscosity, and processingconditions, numerous different constructions can be made. Theseconstructions, along with the material selection, determine theperformance of the final mechanical fastener hook. FIG. 1 shows a firstconstruction of a sheet or web 10 having stems 12. This constructionuses two layers of coextruded material, an upper layer (second layer) 14and a continuous lower elastic layer (first layer) 16. In thisconstruction, more lower layer material is used. The continuous lowerelastic layer 16 forms the base of the sheet, and the core and the upperportion of the stems 12. The upper layer 14 forms a surface layer on thebase of the sheet and around the lower portion of the stems. Inalternative embodiments, a plurality of materials and a plurality ofsublayers can form the respective upper and lower layers 14, 16.

[0034]FIG. 2 shows a construction with more material in the upper layer14 than in the construction of FIG. 1. The continuous lower elasticlayer 16 again forms the base of the sheet 10 and the core of the stems12. Here, the upper layer 14 forms a crown on a stem made from the lowerlayer 16. The upper layer 14 also forms a surface layer on the base ofthe sheet, including a sheath of material surrounding the base of thestem.

[0035] In FIG. 3, the continuous lower elastic layer 16 forms the baseof the sheet 10 and a column of core material for the stems 12. Theupper layer 14 forms the surface layer on the base and on the stems.

[0036] In FIG. 4, the lower elastic layer 16 again forms the continuousbase of the sheet 10 and a small portion of the stems 12. The upperlayer 14 forms the surface layer on the elastic base and forms themajority of the stem material. The lower layer can form any portion ofthe stems to the point at which the upper layer forms the stem basesheet and the stems, and the lower layer is a continuous smooth sheetthat does not form any part of the stems.

[0037]FIG. 5 shows an embodiment similar to FIG. 4. In FIG. 5, thecontinuous elastic lower layer 16 forms the base of the sheet 10 and theupper layer 14 forms the surface layer on the base and forms theentirety of the stem material.

[0038]FIG. 6 shows a stemmed sheet construction using a plurality ofupper layers 18 of material and having a continuous lower elastic layer19. Upper layers 18 could be as few as two layers or scores of differentlayers. These layers can comprise two or more different materials thatcan optionally be repeated in different layers and one or more of thelayers can include a continuous or discontinuous reactive tie layer toincrease interlayer bonding between any two adjacent layers. The elasticbase of the sheet and the stems both are formed of many layers ofmaterial. This construction can result in a product with only onematerial (the uppermost layer) forming the surface layer on the base andforming the outer surface of the stems. Alternatively, as shown, thestems can have a plurality of layers exposed along the length of thestem from the bottom of the stem to the top.

[0039] The layers of the stemmed sheet, before stem formation, can beformed simultaneously or serially, and they can be joined together whileeither or both layers are molten, before the molten layer or layers havecooled. The layers also can be joined together by laminating them toeach other and allowing the layers to cool simultaneously. Optionally,other material, like adhesives and printing can be applied to the webdepending on the intended use and application for the web.

[0040] Serial forming can be accomplished by, for example, sequentialextrusion, first extruding one layer and then extruding another layer.This can be performed with one or more dies. Alternatively, the layerscan be formed in molds or by other known methods such as casting orcalendering. Simultaneous forming can be accomplished by, for example,coextrusion. A single multiple manifold die can be used or a feedblockwhich splits into multiple cavities to create multiple layers can beused.

[0041] Coextrusion can occur by passing different melt streams fromdifferent extruders into (1) a multiple slotted feed block and then intoa single layer film die or (2) a multiple manifold die. In the multipleslotted feed block technique, at least two different materials are fedfrom different extruders into different slots (usually 2 to over 200) ina feed block. The individual streams are merged in the feed block andenter a die as a layered stack that flows out into layered sheets as thematerial leaves the die. The multiple manifold die combines thedifferent molten streams from different extruders at the die lip. Thismethod is usually limited to 2-3 layered films because of the increasedcomplexity as the number of layers is increased. In both cases, thelayered sheet leaving the die is passed between a nip formed by tworolls at least one of which has a tooled surfaced to create stems.

[0042] The layers of the fastener construction may also be laminated toone another under temperature and pressure conditions sufficient toachieve a desired bond strength using techniques well-known in the art.Generally, the layers are heated to a soft state and pressed togetherunder pressure. Temperatures near the melting point of the respectivepolymers and pressures up to 20 KPa or more may be used to generatesatisfactory interlayer adhesion. Alternatively, reactive tie layers,hot melt adhesives and pressure-sensitive adhesives may be used wherehigh temperatures and pressures are undesirable.

[0043] The stem density depends on the application for the product.Densities ranging from 12-465 stem/cm² (81-3000 stems/in²) are mostuseful. Many different stem geometries can be used. Stems can bestraight, angled, or headed (capped). Capped stems can be shaped likemushrooms, golf tees, anchors, or nail heads. They can have an extrudedprofile. Straight stems can: be self mating; have a pressure-sensitiveadhesive (PSA) outer layer; or be subsequently coated with a PSA. Thestems can have any shape including, for example, rods, prisms, spheres,parallelepipeds, irregular angular shapes, and irregular curved shapes.

[0044] The stemmed web can also have a smooth surface with a coextrudedlayer on the smooth side of the web (the side opposite the stems) thatcombines the mechanical fastening function of the stemmed surface withanother function.

[0045] In one embodiment of the invention a fastener construction may bedesigned having a second layer having stems formed of a somewhat brittlethermoplastic material. In such an embodiment the thermoplastic materialcan form a thin skin layer on the continuous elastic base and cancomprise the majority of the stem. This construction provides relativelystiff stems while preserving the overall elastic behavior of theconstruction, which comprises a thin, continuous top layer bearing thestems on a thick elastic layer. The elastic construction can beactivated by stretching. The construction is subjected to sufficientinitial elongation force to break or fracture the skin layer betweenadjacent stems such that the web may thereafter be stretched in betweenthe stiff stems and may return substantially to its original state uponrelease of the stretching force. The stress required for each elongationwill depend on the properties of the elastomeric core, such as modulus,thickness and degree of elongation. Tensile set also depends on thechemistry of the elastomer, and can range from near zero to 50 percent,and in most of the cases between 3 and 10 percent. Stretching ability ofa coextruded stem web depends on the thickness ratio of the layers.Relatively inelastic, stiff polymers that would be suitable for thesecond layer bearing the stems include, for example, polycarbonate andpolystyrene.

[0046] In another embodiment, the second layer bearing stems is made ofan immiscible blend of melt processable polymer materials. As theimmiscible blend is extended through a forming means, such as a die orcalender, into a layer, one of the polymers forms a discontinuous phasewithin a continuous phase of the other polymer. The discontinuous phasepolymer should be melt processable and sufficiently mixed with thecontinuous phase polymer so that the immiscible regions in the extrudedproduct lie within the thickness of the second layer. The discontinuousphase forms (through for example the extrusion process) on a microscopicor molecular scale elongated regions (domains, strands or chains) thatextend in the direction in the second layer, i.e., in the machine ordown-web direction. Generally, the discontinuous polymer regions ordomains should have a cross-sectional diameter in the formed layer ofless than 250 micrometers, preferably less than 100 micrometers, mostpreferably less than 50 micrometers. Such a construction is anisotropicwith regard to elongation.

[0047] The thermoplastic layer separates in multiple striations (bymeans of multiple fractures induced by stretching in the cross-webdirection) within separate regions. That is, discrete regions of thethermoplastic (second) layer are separated when the construction isstretched in a direction that is cross-web or at right angles to themachine direction. As a result, the surface or stem layer breaks intomultiple areas of narrow parallel (fracture) lines between regions wherethe surface layer is intact. In contrast, the thermoplastic (second)layer would separate in a more gross fashion when this type ofconstruction is stretched in the down-web or machine direction. Thesurface (thermoplastic) layer would fracture into larger more randomlyspaced regions. When the surface layer breaks into striations, theconstruction can be stretched to a greater degree and delamination ofthe surface layer around the fractures is not noticeable. However, whenthe surface layer fracture is confined to relatively fewer fracturesthat are separated by much more distance in the down-web direction, theconstruction would not able to stretch as far and delamination would bemore pronounced.

[0048] In another embodiment of the invention, the thermoplastic(second) layer is somewhat ductile. Thus, the thin top layer elongatespermanently during “stretch activation” and folds over or wrinkles on amicroscopic scale during relaxation. Somewhat ductile polymers thatwould be suitable include, for example, polyethylene and polypropylene.

[0049] The maximum thickness of the top (second) layer between the stemsis important. The top layer should not be too thick to prevent stretchactivation of the construction. Actual thickness of the top layerdepends on the size of the stems desired and the force applied toactivate the construction. Generally, thinner top layers are better.Typically, the top layer in the web before stems are formed should beless than 500 microns, preferably less than 250 microns and mostpreferably less than 125 microns.

[0050] Frequently, the minimum thickness of the top layer before stemsare formed is important. The top layer before stems are formed should bethick enough to permit the formation of stems of a desired size andstiffness for a given application. If the material in the elastic layerprovides sufficient support and the material in the top layer issufficiently stiff, the top layer before stem formation can be quitethin because the stems do not need to be composed entirely of thematerial used in the top layer. Conversely, thicker top layers must beused if the stems must be composed entirely of the material of the toplayer. The actual minimum top layer thickness before stem formationdepends on the type of materials used in both principal layers and theapplication.

[0051] These embodiments are illustrated by FIG. 7 and FIG. 8. FIG. 7shows a pre-activated elastic web fastener 10 having stem portions 12made substantially of the second material. The second layer 12, inaddition to forming the stems, is present as a thin coating on top ofthe first continuous elastic layer 16 in between each stem. FIG. 8illustrates the same construction in the extended state upon stretchactivation. Here the web 10 is stretched such that the thin second layer14 has dislocated between the stems by fracturing, allowing the elasticlayer 16 to stretch freely. This construction, upon release of thestretching force, will return substantially to its original orientation,but the dislocations will remain such that the construction will againstretch to the state shown in FIG. 8.

[0052] Various additives may also be incorporated into one or morelayers of the construction, such as fillers (to alter material firmnessand flow properties) or antimicrobial agents or antioxidants (to affectaging properties). Microspheres, flame retardants, internal releaseagents, colorants, thermally conductive particles, and electricallyconductive particles also can be used.

[0053] Hooks can be made by capping the stems to form mushroom heads asdisclosed in U.S. Pat. No. 5,077,870. Also, hooks can be made usingprofile extrusion, forming a long rib on the web. The rib is thenlaterally sliced and then stretched to form a plurality of stems. Headscan be formed on the stems either before or after slicing. This isdisclosed in U.S. Pat. No. 4,894,060.

[0054] The stems may also be shaped to provide directional hookingcapability. Such directional hooks may be used to give directionalstability to a hook and loop fastening construction by providingfastening in a selected direction and releasing capability in theopposite direction. The directional stems can be made by pressing themolten skin layer onto a tool having a plurality of holes that areangled in the same direction. The holes in the tool can be formed with alaser and can be drilled at various angles such as, for example, 450degrees and 600 degrees, with respect to the top surface of the belt.The methodology of laser drilling of a thermoset tool is described inU.S. Pat. No. 5,792,411. These stems do not have to be capped to engagea loop surface. The resulting fastener surface permits the invention tobe cinched tighter by pulling to release mechanical engagement andreleasing to achieve mechanical engagement.

[0055] In one aspect, the loop layer can be elastic if it incorporateselastic fibers that are aligned in one direction. When the constructionis stretch-activated, cracks or fissures appearing in the hard (orinelastic second) layer that bears the stems become permeable to air andmoisture. Since the elastic layer is already gas and moisture permeable,the entire construction is breathable after activation (i.e. it ispermeable to gases and vapors).

[0056] The stemmed webs of this invention can be used in virtually anyapplication as any other stemmed web, and find particular utility in theconstruction of compression wrap article or bandage that can be used inorthopedic applications. For example, elastic fasteners can be used aselastic wraps to secure cables, orthopedic articles or athleticprotective devices. Medical wraps or bandages can be made to possess thestrength, elasticity, and fastening properties required for a particularutility without the disadvantages associated with the use of cohesiveand adhesive medical wraps and bandages.

[0057] This invention is further illustrated by the following examplesthat are not intended to limit the scope of the invention. In theexamples, all parts, ratios and percentages are by weight unlessotherwise indicated. The following test methods were used tocharacterize the articles in the examples:

Test Methods

[0058] Interlayer Adhesion

[0059] The interlayer adhesion between the materials of thethermoplastic layer and the materials of the elastic layer was measuredon samples without stems made in a platen press. For each example, theadhesion between layers of these materials was measured by performingtensile, T-peel tests using a Model 1122 Instron apparatus, availablefrom Instron Corporation, Canton, Mass. The width of the samples were 25mm, and crosshead speed was 100 mm/minute.

[0060] Layer Thickness

[0061] The thickness of the layers in the samples were measured using aModel EG-233 Ono Sokki Digital Linear Gauge equipped with a Model ST-022Gauge Stand, available from Ono Sokki Company, Ltd., Japan. An opticalmicrograph of a cross-section of a sample of film having stems on asurface was taken using an optical microscope with photographiccapability, available from Leeds Precision Instruments, Minneapolis,Minn. Materials Used Material Description DOWLEX ™ 3445 Polypropylene,melt index 35 g/10 min., available from Dow Chemical Co., Midland, MI.VECTOR ™ 4111 Styrene-isoprene-stryene block co-polymer available fromExxon Chemical Co., Houston, TX. STYRON ™ 615 Polystyrene available fromDow Chemical Co., Midland, MI. BYNEL ™ XB602 Polypropylene with 1 wt %epoxy functional groups grafted thereon, available from DuPont Company,Wilmington, DE. KRATON ™ FG- Styrene-ethylene/butylene-styrene block co-1901X polymer with 1 wt % succinic anhydride, available from ShellChemical Co., Houston, TX. LOTADER ™ Copolymer of polyethylene and 8 wt.% AX8840 glycidylmethacrylate, available from Elf Atochem Co.,Philadelphia, PA KRATON ™ G1657 Styrene-ethylene/butylene-styrene blockco- polymer, available from Shell Chemical Co., Houston, TX. CD1010Triarylsulfoniumbexafluoroantimonate, available from Sartomer, Exton,Pennsylvania ESTANE ™ 58661 Polyurethane, tensile set of 3% whenstretched 200%, shore hardness 85A, available from B. F. Goodrich,Cleveland, OH TECOFLEX ™ CLC- Polyurethane, shore hardness 70D,available from 60D Thermedics Co., Spartanburg, SC. DYPRO ™ 7825MZPolypropylene with a melt flow index of 35 available from Fina Oil &Chemical Co. Dallas, Texas. G18 Polystyrene with a melt flow index of 18available from Huntsman Chemical Corp. Chesapeake, Virginia LoopMaterial A Non-woven sheet of polypropylene spun-bond and crimped loopmaterial attached to a layer of KRATON ™ G1657 polymer which wasattached to a thin layer of polypropylene and prepared according to U.S.Pat. No. 5,256,231. Loop Material B Woven sheet of Polyester Style695738, available from Milliken and Company, Spartanburg, SC. LoopMaterial C Non-woven sheet consisting of parallel strands of SPANDEXfibers sandwiched between two layers of polypropylene spun-bond loopmaterial, pre- pared by a means such that the SPANDEX fibers are intension when the outer polypropylene spun bond material is applied toit.

Example 1

[0062] DOWLEX™ 3445 polypropylene, was fed into a single screw extruderhaving a diameter of about 32 mm, an L/D of 24/1, a screw speed of 15rpm and a temperature profile that rose up to approximately 215° C. Thethermoplastic material was passed through the extruder and continuouslydischarged at a pressure of at least 0.7 MPa through a heated neck tubeand into one port in a three-layer adjustable vane feed block (Cloeren™Model 86-120-398, available from Cloeren Co. and setup for two layers)that was mounted on a 25.4 cm wide film die (Cloeren™ EBR III 96-151also available from Cloeren Co.). An elastic material, Vector 4111, wasfed into a second single screw extruder having a diameter of about 64mm, an L/D of 24/1, a screw speed of 5 rpm and a temperature profilethat steadily increased to approximately 215° C. The elastic materialwas then continuously discharged at a pressure of at least about 1.4 MPathrough a heated neck tube and into a second port in the three-layerfeed block. The feed block and die were set at approximately 215° C. Thedie gap was set at approximately 0.5 mm. The two layer moltenconstruction was discharged from the die and drop fed at about 1.5 m/mininto a nip formed by two rolls having a nip pressure of about 0.2 KPa.The first roll had a tooled surface that was maintained at 55° C. andcontained cavities with diameters of about 280 microns, depths in excessof about 2.5 mm and spacing of about 813 microns, resulting in a stemarray having a stem density of about 140 stems/cm². The second roll hada smooth chrome-plated surface that was also maintained at 55° C. Thepolypropylene layer faced the tooled surface and the elastic layer facedthe chrome surface. The resulting cast film was removed from the tooledsurface to form a stem-surfaced film with rod-like stem projections,each having a diameter of approximately 300 microns and a height ofabout 700 microns, extending from the surface of the film. Caps wereformed on the stems on part of the film by exposing the surface havingstems to a roll heated to 138° C. The elastic side of the cappedstem-surface film coated with LSE 300 acrylic based TransferPressure-Sensitive Adhesive, available from 3M, and laminated onto asheet of Loop Material A.

[0063] Measurements were made on the film and a pressed sandwich madefrom similar materials, and the film was stretched at various lengthsand observed. The adhesion between the hard and elastic layers wasapproximated by measuring Interlayer Adhesion on a pressed laminate madewith similar materials that were pressed together in a Wabasha™ pressthat had been heated to 204° C. The interlayer adhesion for a laminateof these materials was 270 N/m. Elastic material was observed by opticalmicroscopy to comprise the central part of the stems. The thickness ofthe hard layer and the elastic layer was measured to be about 20 and 100microns (μm), respectively. Three samples of film were stretched either(1) to 400% beyond the sample's original length at one time, (2) 400% in100% increments or (3) 50%. Upon stretching up to 400%, thethermoplastic layer between the stems permanently deformed in all threecases. Upon relaxing the film, the stem-surfaced film retracted about80% of it's elongation such that about 20% of the extension was apermanent elongation and the hard layer was observed to form a multitudeof folds or ripples between the stems. Subsequent elongation andrelaxation cycles resulted in only slight increases in permanentelongation. When the film was stretched and wrapped around onto itself,a mechanical bond was formed upon contact between the capped stemsurface and the loop surface. No delamination between the layers ofmaterial was observed.

Example 2 and Comparative Example 1

[0064] These examples illustrate the effect of increasing the thicknessof the thermoplastic (second) layer on performance of the inventive web.

[0065] In Example 2 and Comparative Example 1, a film having a surfacewith a multiplicity of uncapped stems without loop material was made ina manner similar to that of Example 1 except that flow rate of the hard(thermoplastic) material was increased to result in an increasedthickness in the second layer of 50 and 80 μm, respectively. The web ofExample 2 was like FIG. 3, and the web of Comparative Example 1 was likeFIG. 5.

[0066] For each example, the stem-surfaced film performance was observedduring stretching. Example 2 was stretched up to about 20% before thethermoplastic film fractured. During the elongation, the hard layerdeformed until fracture occurred at 20% elongation. The hard layer didnot appear to delaminate from the elastic layer. In Comparative Example1, the film broke with negligible stretching. The hard layer and theelastic layer exhibited some delamination and the thickness of the hardlayer made with this material was too thick to permit any elasticmaterial to flow into the stems and form a bond.

Example 3

[0067] These examples illustrate the effect of increasing the thicknessof a different hard layer on performance of the stem-surfaced film.

[0068] In Example 3, the film having stems without caps on its surfaceand without loop material on the other side was made in a manner similarto that of Example 1 except that the second layer material was Styron615 polystyrene, and the flow rate of the hard material was increased toresult in an increased thickness in the second layer to 20 μm. Theextruder temperature was kept the same as in Example 1.

[0069] For each example, the stem-surfaced film performance was observedduring stretching. Example 3 was stretched up to about 50% before thepolystyrene film broke. During the elongation, microfractures formed inthe polystyrene layer between the stems which separated with increasedelongation.

Examples 4 and 5

[0070] These examples illustrate the effect of using reactive tie layersand increasing the number of stems per unit area on performance of thestem-surfaced film.

[0071] In Examples 4 and 5, the film having a surface with uncappedstems without loop material was made in a manner similar to that ofExample 1 except reactive tie layers were present, and differentmaterials and hole number densities in the tooled surface were used. Inboth Example 4 and 5, the hard material and the elastic material wereBynel™ XB602 polypropylene and Kraton™ FG-1901X copolymer, respectively.The tie layer was the reaction product of the epoxy functional groups inthe hard layer and the succinic anhydride in the elastic layer. InExample 4 and 5, the tooled surface was changed to create a stem densityof about 208 stems/cm² and 480 stems/cm².

[0072] For each example, the adhesion between layers of these materialswas measured and the performance of the inventive web was observedduring stretching. The interlayer adhesion was 1090 N/m. The stems wereobserved to consist of only hard material even though the layerthickness was 20 μm because the melt viscosity of the elastic materialwas much higher than that of the thermoplastic material and thus did notflow into the holes of the tooled surface. However, the hard and elasticlayers were not observed to delaminate when the stem-surfaced films ofboth example 4 and 5 were stretched as in Example 1 even though therewas no mechanical engagement between the layers. Increased stem numberdensity, which would be expected to create stronger mechanical bonds,did not have any adverse effects on the stretch performance.

Examples 6-10

[0073] These examples illustrate the effect of using reactive tie layersand radiation crosslinking on performance of the stem-surfaced film.

[0074] In Examples 6-10, the two-layer films of thermoplastic andelastic layers were made with a Model 030H-15-LP Wabash Hot Pressequipped with platen plates available from Wabash MPI, Wabash, Ind. InExample 6 thermoplastic layers and elastic layers were individually madeof thermoplastic material, Lotader™ AX8840, and elastic material,Kraton™ G1657, respectively. The Lotader AX8840 polymer layer was formedby placing the material under a temperature of 204° C. and a pressure of276 KPa for 1.5 minutes between the platten plates that were coveredwith polytetrafluoroethylene coated sheets. The Kraton™ G1657 layer wasformed by placing the material under a temperature of 204° C. and apressure of 827 kPa for 1.5 minutes between the platten plates that werecovered with a polyimide based liner. The two layers were then pressedtogether under a temperature of 180° C. and slight contact pressure for30 seconds. Immediately following heating, the two layer constructionwas rolled twice with a two pound roller. Example 7 was made as Example6 except the elastic material was Kraton™ G1901. Example 8 was made asExample 7 except the two-layer film was (1) placed in an oven for 30seconds that was preheated to 180° C. and (2) irradiated withultraviolet light on a conveyor web line. The ultraviolet light curingsystem included a Model F600V curing system and EPIQ 6000 Irradiator,both available from Fusion UV Curing Systems, Gaithersburg, Md. Thesurface of the film was exposed to 2 J/cm² of radiation as measured by aUV Power Puck™, available from EIT, Sterling, Va. Example 9 was made asin Example 8 except the elastic layer contained 0.5 wt % Ph₃SSbF₆catalyst. Example 10 was made like Example 9 except the amount ofcatalyst was 1.0 wt % and the two-layer film was preheated for 3 minutesbefore UV irradiation.

[0075] For each example, the adhesion between layers of these materialswas measured and reported below. TABLE 1 Interlayer Adhesion Example(N/m) 6  270 7  305 8 1090 9 1140 10  2040

[0076] As seen in Table 1, the interlayer adhesion can be dramaticallyaffected by the presence of actinic radiation sensitive catalysts.Increased interlayer adhesion decreases the need for interlayer adhesionvia mechanical entanglement of the two principal layers, thus permittingstiffer stems to be made that do not contain any elastic material.

Examples 11 and 12

[0077] These examples illustrates the effect of using a pair ofmaterials that differ primarily in hardness on performance of thestem-surfaced film.

[0078] In Examples 11 and 12, the film having a surface bearing stemswithout loop material was made in a manner similar to that of Example 1except the materials and some process conditions were different. Thesecond layer material and the elastic material in both examples wereTECOFLEX™ CLC-60D polyurethane and ESTANE™ 58661polyurethane,respectively. The flow rates were such that the hard layer and theelastic layer for Examples 11 and 12 were 20 and 100 μm and 10 and 100μm, respectively.

[0079] Example 11 was stretched 20% before the second layer film broke.The permanent elongation was 10% upon the initial release. Example 12could be stretched 30% without fracturing of the Tecoflex CLC-60Dpolyurethane or delamination of the layers.

Examples 13 and 14

[0080] Another method of making the inventive elastic stem-surfacedfastener:

[0081] Examples 13 and 14 were made similar to Example 1 except thelayer containing loops was applied in a different manner. In Example 13,Loop Material B was passed between the nip between the tooled surfaceand the smooth surface with the molten two-layer film, both at about 1.5m/min. An adhesive bonding layer was not needed because the molten filmbecame sufficiently embedded into one woven fiber surface of the LoopMaterial B construction. Example 14 was made as Example 13 except theVector 4111 elastic copolymer was absent from the process and LoopMaterial C was used instead of Material B.

[0082] The fastener constructions of both examples were stretchactivated by elongating the web in three different directions, (1)down-web, (2) 30° from down-web and (3) cross-web. Because of theanisotropic characteristics of the loop material used, the constructionswere able to be stretched 150% in the first case, 40% in the second caseand only 10% in the third case. Both examples could be wrapped around anobject in the stretched condition and mechanically fastened.

Example 15

[0083] The effect of self-mating stems on both sides was demonstrated.

[0084] The web of Example 15 was made in a manner similar to that ofExample 1 except the thermoplastic second layer material was fed intoboth the first and third slot of the feed block, both surfaces of thenip were tooled with holes, capping was done at 180° C. and no loopmaterial was used.

[0085] Each side of the resulting film was able to engage the other sidewithout the use of loops after the film had been stretched at least 20%.

Example 16

[0086] The effect of stem hook directionality on performance wasdemonstrated. Web having stems on a surface was made in a manner similarto Example 1 except that a tooled surface having a different pattern wasused and the stems were not capped. The holes in the tooled surface weremade at an angle to the surface of the tool rather than normal to thesurface. Two samples were made, Sample A with holes in the tooledsurface roll such that stems were formed in the vertical plane of themoving web and at an angle of 45 degrees back toward the die and SampleB at an angle of 60 degrees. The resulting stem-surfaced webs werelaminated to Loop Material A. The resulting elastic structures werecapable of being cinched, i.e. disengaging the mechanical fasteningelements when stretched under tension and re-engaging them withincreased binding pressure when the film was released.

Example 17

[0087] The effect of anisotropic elasticity on performance wasdemonstrated.

[0088] A three layer film was prepared on a co-extrusion film line using3 extruders. The A and C layers (first and second skin layers or outerlayers) were extruded using 3.8 cm diameter single screw extruders (24:1L/D) manufactured by Davis-Standard Corp. Cedar Grove, N.J. havingbarrel zone temperature profiles of 177° C.-204° C.-218° C.-246° C. andscrew speeds of 23 rpm. The compositions of the A layer and the B layerwere the same and consisted of a blend of DYPRO™ 7825MZ polypropyleneand G18 polystyrene in a weight ratio of 25:75. The B layer (elastomericcore) was extruded with a 6.35 cm diameter single screw extruder (24:1L/D) manufactured by Davis-Standard Corp. Cedar Grove, N.J. using abarrel zone temperature profile of 177° C.-204° C.-218° C.-246° C. and ascrew speed of 30 rpm. KRATON™ GI657 copolymer was used for the B layer.The A, B, and C polymer streams were combined in a Cloeren ABC feedblock(Cloeren Co., Orange, Tex.) and then extruded through a conventionalcoat hanger die. The feedblock and die were maintained at a temperatureof 260° C. The 3 layer film was extruded into a nip formed with a chromeroll and a temperature controlled tooled surface with the C layer beingin contact with the tooled surface. The tooled surface contained stemforming cavities at a density of 388/cm². The chrome roll was maintainedat a temperature of 7° C. and the tooled surface was maintained at atemperature of 66° C. The 3 layer film was stripped from the tooledsurface and wound into a roll. The resulting film had a base filmthickness of 163 microns with upstanding stems formed from the C layerprojecting from the base film having heights of about 550 microns anddiameters of about 226 microns (measured about 150 microns above thebase film face). The film was then fed through a 406 micron gap betweenan upper (133° C.) calender roll and lower (43° C.) backup roll suchthat the upper roll would contact the distal ends of the stems and heatthem to a temperature at which they readily deform under mechanicalpressure, resulting in generally uniform disc shaped heads havingdiameters of 330 microns.

[0089] Samples of the resulting film were cut into strips approximately3 cm long and 2.5 cm wide. Sample A had its long dimension in themachine direction and Sample B had its long dimension in the cross-webdirection. Both were stretched in the long dimension to activate theconstruction. The stem-surface of Sample A fractured into a singlejagged line across the strip. Further stretching resulted in a secondand a third fracture across the strip between regions of unbrokensurface measuring between 1 and 3 cm long. Delamination was observedbetween the thermoplastic stem surface layer and the elastic layer. Thesurface of Sample B having stems fractured into several regions ofstriations across the strip. Delamination was not observed.

We claim:
 1. A method of making a web material having a plurality ofstems extending from at least one side of the web, comprising the stepsof melt forming two layers and forming a plurality of stems on at leastone surface, which method is characterized by: (a) melt forming, from anelastomeric material, a first layer (16) having a first surface and asecond surface; (b) melt forming, from a second material, a continuoussecond layer (14) having a first surface and a second surface; (c)joining the first surfaces of first and second layers to form a sheetwherein said first layer is continuous; and (d) forming a plurality ofstems (12) on at least the second surface of the second layer (14) ofmaterial.
 2. The method of claim 1 wherein said elastomeric materialcomprising said first layer is selected from the group consisting of:natural and synthetic rubbers, styrene block copolymers containingisoprene, butadiene, or ethylene(butylenes) blocks,metallocene-catalyzed polyolefins, polyurethanes andpolydiorganosiloxanes, and said second material comprises athermoplastic material.
 3. The method of claim 2 wherein saidthermoplastic material is selected from the group consisting of:polyolefins, polystyrenes, polycarbonates, polymethyl methacrylate,ethylene vinyl acetate copolymers, acrylate modified ethylene vinylacetate polymers, and ethylene acrylic acid copolymers.
 4. The method ofclaim 1 further comprising adding a reactive tie layer between the firstand the second layers, said reactive tie layer being selected from thegroup consisting of (1) the reaction product of reactive functionalitiesin the first and second layers that react where the first side of thefirst layer contacts the first side of the second layer and (2) apolymer comprising segments that have preferential affinity for thematerial of the first layer or material of the second layer.
 5. Themethod of claim 1 further comprising coating an adhesive material on atleast a portion of said stems.
 6. The method of claim 1 furthercomprising applying at least one additional layer to the outer surfaceof the multiple layer sheet wherein said additional layer has a surfacebearing a multiplicity of loops.
 7. The method of claim 1 wherein thestem forming step comprises pressing the sheet from step (c) against atleast one temperature controlled surface containing an array of holes toform an array of stems.
 8. The method of claim 7 further comprisingforming caps on one or more of the stems by pressing the stems against aheated surface to form caps on the tips of the stems.
 9. The method ofclaim 1 wherein the stem forming step comprises: (1) passing the sheetfrom step (c) through a shaped die to form a plurality of raised ribs onat least one surface of the multiple layer sheet; (2) passing aplurality of sharp edges perpendicularly through the ribs; and (3)stretching the multiple layer sheet to separate each rib into aplurality of stems.
 10. The method of claim 1 wherein step (d) comprisesforming the plurality of stems of at least the second material and themethod further comprises the step of selecting relative quantities ofthe first and second materials such that the fist material which formsthe first layer protrudes into or through and forms part of the stemsformed on the second surface of the second layer.